High plasma soluble prorenin receptor (sPRR) is associated with vascular damage in male but not female mice fed a high fat diet

Plasma soluble prorenin receptor (sPRR) displays sexual dimorphism and is higher in women with type 2 diabetes mellitus (T2DM). However, the contribution of plasma sPRR to the development of vascular complications in T2DM remains unclear. We investigated if plasma sPRR contributes to sex differences in the activation of the systemic renin-angiotensin-aldosterone system (RAAS) and vascular damage in a model of high-fat diet (HFD)-induced T2DM. Male and female C57BL/6J mice were fed either a normal fat diet (NFD) or an HFD for 28 weeks to assess changes in blood pressure, cardiometabolic phenotype, plasma prorenin/renin, sPRR, and Ang II. After completing dietary protocols, tissues were collected from males to assess vascular reactivity and aortic reactive oxygen species (ROS). A cohort of male mice was used to determine the direct contribution of increased systemic sPRR by infusion. To investigate the role of ovarian hormones, ovariectomy (OVX) was performed at 32 weeks in females fed either a NFD or HFD. Significant sex differences were found after 28 weeks of HFD, where only males developed T2DM and increased plasma prorenin/renin, sPRR, and Ang II. T2DM in males was accompanied by non-dipping hypertension, carotid artery material stiffening, and aortic ROS. sPRR infusion in males induced vascular thickening instead of material stiffening caused by HFD-induced T2DM. While intact females were less prone to T2DM, OVX increased plasma prorenin/renin, sPRR, and SBP. These data suggest that sPRR is a novel indicator of systemic RAAS activation and reflects the onset of vascular complications during T2DM regulated by sex.

Sex differences in soluble prorenin receptor in patients with type 2 diabetes

BACKGROUND

The soluble prorenin receptor (sPRR), a member of the renin-angiotensin system (RAS), is elevated in plasma of patients with preeclampsia, hypertension, chronic kidney disease (CKD), and type 2 diabetes. Our goal was to examine the relationship between sPRR and RAS activation to define whether sexual dimorphisms in sPRR might explain sex disparities in renal outcomes in patients with type 2 diabetes.

METHODS

Two hundred sixty-nine participants were included in the study (mean age, 48 ± 16 years; 42% men, 58% women), including 173 controls and 96 subjects with type 2 diabetes. In plasma and urine, we measured sPRR, plasma renin activity (PRA), and prorenin. In the urine, we also measured angiotensinogen along with other biomarkers of renal dysfunction.

RESULTS

Plasma sPRR and PRA were significantly higher in women with type 2 diabetes compared to men. In these women, plasma sPRR was positively correlated with PRA, age, and body mass index (BMI). In contrast, in men the sPRR in urine but not in plasma positively correlated with eGFR in urine, but negatively correlated with urine renin activity, plasma glucose, age, and BMI.

CONCLUSIONS

In patients with type 2 diabetes, sPRR contributes to RAS stimulation in a sex-dependent fashion. In diabetic women, increased plasma sPRR parallels the activation of systemic RAS; while in diabetic men, decreased sPRR in urine matches intrarenal RAS stimulation. sPRR might be a potential indicator of intrarenal RAS activation and renal dysfunction in men and women with type 2 diabetes.

Exercise-Induced Modulation of Angiotensin II Responses in Femoral Veins From 2-Kidney-1-Clip Hypertensive Rats

The present study investigated the angiotensin II (Ang II) responses in rat femoral veins taken from 2-kidney-1clip (2K1C) hypertensive rats at 4 weeks after clipping, as well as the effects of exercise on these responses. In this manner, femoral veins taken from 2K1C rats kept at rest or exposed to acute exercise or to exercise training were challenged with Ang II or endothelin-1 (ET-1) in organ bath. Simultaneously, the presence of cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) were determined in these preparations by western blotting. In these experiments, femoral veins exhibited subdued Ang II responses. However, after nitric oxide (NO) synthesis blockade, the responses were higher in the femoral veins taken from animals kept at rest [0.137(0.049–0.245); n = 10] than those obtained in trained animals kept at rest [0.008(0.001–0.041); n = 10] or studied after a single bout of exercise [0.001(0.001–0.054); n = 11]. In preparations in which, in addition to NO synthesis, both the local production of prostanoids and the action of ET-1 on type A (ET_A) or B (ET_B) receptors were inhibited, the differences induced by exercise were no longer observed. In addition, neither ET-1 responses nor the presence of COX-1 and COX-2 in these preparations were modified by the employed exercise protocols. In conclusion, NO maintains Ang II responses reduced in femoral veins of 2K1C animals at rest. However, vasodilator prostanoids as well as other relaxing mechanisms, activated by ET_B stimulation, are mobilized by exercise to cooperate with NO in order to maintain controlled Ang II responses in femoral veins.

Urinary angiotensinogen increases in the absence of overt renal injury in high fat diet-induced type 2 diabetic mice

AIM OF THE STUDY

During type 2 diabetes (T2D) and hypertension there is stimulation of renal proximal tubule angiotensinogen (AGT), but whether urinary excretion of AGT (uAGT) is an indicator of glomerular damage or intrarenal RAS activation is unclear. We tested the hypothesis that elevations in uAGT can be detected in the absence of albuminuria in a mouse model of T2D.

METHODS

Male C57BL/6 mice (N = 10) were fed a high fat (HFD; 45% Kcal from fat) for 28 weeks, and the metabolic phenotype including body weight, blood pressures, glucose, insulin, ippGTT, HOMA-IR, and cholesterol was examined. In addition, kidney Ang II content and reactive oxygen species (ROS) was measured along with urinary albumin, creatinine, Ang II, and AGT.

RESULTS

All parameters consistent with T2D were present in mice after 12-14 weeks on the HFD. Systolic BP increased after 18 weeks in HFD but not NFD mice. Intrarenal ROS and Ang II concentrations were also increased in HFD mice. Remarkably, these changes paralleled the augmentation uAGT excretion (3.66 ± 0.50 vs. 0.92 ± 0.13 ng/mg by week 29; P < 0.01), which occurred in the absence of overt albuminuria.

CONCLUSIONS

In HFD-induced T2D mice, increases in uAGT occur in the absence of overt renal injury, indicating that this biomarker accurately detects early intrarenal RAS activation.

Abstract 073: The Association Between Plasma Soluble Prorenin Receptor and Renin Activity Points Toward Renin Angiotensin System Activation and Cardiovascular Complications in Women With Type-2 Diabetes

Activation of the renin-angiotensin system (RAS) increases the risk of hypertension and chronic kidney disease (CKD) in patients with type 2 diabetes mellitus (T2DM). The prorenin receptor (PRR), a component of the RAS, activates prorenin via a non-catalytic mechanism. High levels of the soluble form of PRR (sPRR) have been reported in patients with cardiovascular (CV) diseases, including essential hypertension, CKD, preeclampsia, and gestational diabetes. Increased systemic prorenin in T2DM subjects raises the concern whether CV complications are due to augmented levels of plasma sPRR. To test the hypothesis that increased plasma sPRR is associated with systemic RAS activation, CV complications, and decline in renal function, we measured plasma sPRR, plasma renin activity (PRA), and biomarkers of renal dysfunction in 269 patients (mean age, 48 ± 1 years; 42% men, 58% women), including 173 controls (CT) and 96 patients with T2DM. Plasma sPRR levels measured by ELISA were higher in T2DM patients (19.2 ± 7.6 ng/mL) compared with CT (16.5 ± 0.4 ng/mL; p<0.001). Plasma levels of sPRR contrasted between T2DM and CT patients of same sex (Women: 20 ± 1.11 vs. 15.3 ± 0.3 ng/mL; p<0.001; Men: 17 ± 1 vs. 18 ± 0.5 ng/mL; p=0.18). PRA was augmented in T2DM patients, including Men: 9.8 ± 3,6 vs. Ang I/mL/hr; p<0.001, and even greater in Women: 13.5 ± 1.1 vs. 3.1 ± 0.3 Ang I/mL/hr; p<0.001. Increases in sPRR and PRA paralleled with hypertension, declined eGFR, and albumin/creatinine ratio in T2DM patients. Interestingly, PRA was positively correlated with plasma sPRR in women (r=0.49; p<0.001) but not in men (r=0.15 1; p=0.207). Multiple regression analysis, adjusted by age, BMI, and groups supports the association between plasma sPRR and T2DM status in women (p<0.001) but not in men. In conclusion: 1) Plasma sPRR is associated with PRA in T2DM women but not in men; and 2) The association between sPRR and PRA predisposes women with T2DM to systemic RAS activation and CV complications, as hypertension and CKD. Plasma sPRR reflects systemic RAS activation and has the potential to be a biomarker of T2DM and CV complications, particularly in women.

Effects of serelaxin on renal microcirculation in rats under control and high-angiotensin environments

Serelaxin is a novel recombinant human relaxin-2 that has been investigated for the treatment of acute heart failure. However, its effects on renal function, especially on the renal microcirculation, remain incompletely characterized. Our immunoexpression studies localized RXFP1 receptors on vascular smooth muscle cells and endothelial cells of afferent arterioles and on principal cells of collecting ducts. Clearance experiments were performed in male and female normotensive rats and Ang II-infused male rats. Serelaxin increased mean arterial pressure slightly and significantly increased renal blood flow, urine flow, and sodium excretion rate. Group analysis of all serelaxin infusion experiments showed significant increases in GFR. During infusion with subthreshold levels of Ang II, serelaxin did not alter mean arterial pressure, renal blood flow, GFR, urine flow, or sodium excretion rate. Heart rates were elevated during serelaxin infusion alone (37 ± 5%) and in Ang II-infused rats (14 ± 2%). In studies using the in vitro isolated juxtamedullary nephron preparation, superfusion with serelaxin alone (40 ng/ml) significantly dilated afferent arterioles (10.8 ± 1.2 vs. 13.5 ± 1.1 µm) and efferent arterioles (9.9 ± 0.9 vs. 11.9 ± 1.0 µm). During Ang II superfusion, serelaxin did not alter afferent or efferent arteriolar diameters. During NO synthase inhibition (l-NNA), afferent arterioles also did not show any vasodilation during serelaxin infusion. In conclusion, serelaxin increased overall renal blood flow, urine flow, GFR, and sodium excretion and dilated the afferent and efferent arterioles in control conditions, but these effects were attenuated or prevented in the presence of exogenous Ang II and NO synthase inhibitors.

Collecting duct prorenin receptor knockout reduces renal function, increases sodium excretion, and mitigates renal responses in ANG II-induced hypertensive mice

Augmented intratubular angiotensin (ANG) II is a key determinant of enhanced distal Na⁺ reabsorption via activation of epithelial Na⁺ channels (ENaC) and other transporters, which leads to the development of high blood pressure (BP). In ANG II-induced hypertension, there is increased expression of the prorenin receptor (PRR) in the collecting duct (CD), which has been implicated in the stimulation of the sodium transporters and resultant hypertension. The impact of PRR deletion along the nephron on BP regulation and Na⁺ handling remains controversial. In the present study, we investigate the role of PRR in the regulation of renal function and BP by using a mouse model with specific deletion of PRR in the CD (_CDPRR-KO). At basal conditions, _CDPRR-KO mice had decreased renal function and lower systolic BP associated with higher fractional Na⁺ excretion and lower ANG II levels in urine. After 14 days of ANG II infusion (400 ng·kg^-1·min^-1), the increases in systolic BP and diastolic BP were mitigated in _CDPRR-KO mice. _CDPRR-KO mice had lower abundance of cleaved αENaC and γENaC, as well as lower ANG II and renin content in urine compared with wild-type mice. In isolated CD from _CDPRR-KO mice, patch-clamp studies demonstrated that ANG II-dependent stimulation of ENaC activity was reduced because of fewer active channels and lower open probability. These data indicate that CD PRR contributes to renal function and BP responses during chronic ANG II infusion by enhancing renin activity, increasing ANG II, and activating ENaC in the distal nephron segments.

Abstract P198: Increased Urinary Angiotensinogen Reflects Intrarenal Renin-angiotensin System Activation in High Fat Diet Induced-type 2diabetic Mice

Obesity is a risk factor for diabetes mellitus (DM) and patients with DM are often hypertensive and exhibit inappropriate activation of the intrarenal renin-angiotensin system (RAS), which increases the risk for diabetic nephropathy and progression to chronic kidney disease. Enhanced intrarenal AGT levels contribute to increased intrarenal Angiotensin II levels. To examine the role of an activated RAS in DM, we measured urinary AGT along with albuminuria and other metabolic parameters in high fat diet induced-type 2 DM mice. Immediately after weaning, male C57BL/6J mice (N=18) were fed either a normal fat diet (18 % Kcal from fat; CT mice) or high fat diet (42.0 % Kcal from fat; HF mice) for 24 wk. Body weight (BW), food intake, and systolic blood pressure (SBP) by telemetry, were measured weekly. Glucose tolerance test (GTT) and homeostasis model assessment index of insulin resistance (HOMA-IR) were further assayed. At wks 0, 12, and 24 on dietary regimen, measurements of albuminuria and uAGT by ELISA were used as markers of renal injury and intrarenal RAS activation, respectively. Body weight increased by 140% in HF mice compared to 66 % in CT mice (from 18±0.5 to 44±1.4 g and 17±0.6 to 28±0.6 g, respectively) with no differences in daily energy intake (15.02±1.3 kcal/day and 15.4±0.8 kcal/day). Plasma glucose, area under curve (AUC) of GTT, and HOMA-IR were significantly increased in HF mice (121± 6mg/dL; 32,865±6,222; 5±1) compared to CT mice (220± 27mg/dL; 55,549±4,611; 54±9). In HF mice, SBP was augmented by wk 10 compared to CT mice (126±5 vs. 113±1 mmHg; P<0.05). Interestingly, no differences in albuminuria were found between HF and CT mice either at wk 12(50±13 vs. 40±6 ug/day) or at wk 24 (57±7 vs. 43±3 ug/day). However, uAGT excretion was increased by wk 24 in HF mice but not in CT mice ( wk 0 : 4±1.5 vs. 4±1.5ng/day; wk 12 : 4.6±2.3 vs. 2.3±0.9 ng/day; wk 24 : 11.8±2.9 vs. 3.9±0.3 ng/day; P<0.05). During HF diet induced-type 2 DM, the elevation of uAGT reflects the increase of intrarenal RAS which may contribute to the development of renal injury.

Increased angiotensinogen expression, urinary angiotensinogen excretion, and tissue injury in nonclipped kidneys of two-kidney, one-clip hypertensive rats

In angiotensin II (ANG II)-dependent hypertension, there is an angiotensin type 1 receptor-dependent amplification mechanism enhancing intrarenal angiotensinogen (AGT) formation and secretion in the tubular fluid. To evaluate the role of increased arterial pressure, AGT mRNA, protein expression, and urinary AGT (uAGT) excretion and tissue injury were assessed in both kidneys of two-kidney, one-clip Sprague-Dawley hypertensive rats subjected to left renal arterial clipping (0.25-mm gap). By 18-21 days, systolic arterial pressure increased to 180 ± 3 mmHg, and uAGT increased. Water intake, body weights, 24-h urine volumes, and sodium excretion were similar. In separate measurements of renal function in anesthetized rats, renal plasma flow and glomerular filtration rate were similar in clipped and nonclipped kidneys and not different from those in sham rats, indicating that the perfusion pressure to the clipped kidneys remained within the autoregulatory range. The nonclipped kidneys exhibited increased urine flow and sodium excretion. The uAGT excretion was significantly greater in nonclipped kidneys compared with clipped and sham kidneys. AGT mRNA was 2.15-fold greater in the nonclipped kidneys compared with sham (1.0 ± 0.1) or clipped (0.98 ± 0.15) kidneys. AGT protein levels were also greater in the nonclipped kidneys. The nonclipped kidneys exhibited greater glomerular expansion and immune cell infiltration, medullary fibrosis, and cellular proliferation than the clipped kidneys. Because both kidneys have elevated ANG II levels, the greater tissue injury in the nonclipped kidneys indicates that an increased arterial pressure synergizes with increased intrarenal ANG II to stimulate AGT production and exert greater renal injury.

Prenatal exposure to cannabis and maternal and child health outcomes: a systematic review and meta-analysis

OBJECTIVE

To assess the effects of use of cannabis during pregnancy on maternal and fetal outcomes.

DATA SOURCES

7 electronic databases were searched from inception to 1 April 2014. Studies that investigated the effects of use of cannabis during pregnancy on maternal and fetal outcomes were included.

STUDY SELECTION

Case-control studies, cross-sectional and cohort studies were included.

DATA EXTRACTION AND SYNTHESIS

Data synthesis was undertaken via systematic review and meta-analysis of available evidence. All review stages were conducted independently by 2 reviewers.

MAIN OUTCOMES AND MEASURES

Maternal, fetal and neonatal outcomes up to 6 weeks postpartum after exposure to cannabis. Meta-analyses were conducted on variables that had 3 or more studies that measured an outcome in a consistent manner. Outcomes for which meta-analyses were conducted included: anaemia, birth weight, low birth weight, neonatal length, placement in the neonatal intensive care unit, gestational age, head circumference and preterm birth.

RESULTS

24 studies were included in the review. Results of the meta-analysis demonstrated that women who used cannabis during pregnancy had an increase in the odds of anaemia (pooled OR (pOR)=1.36: 95% CI 1.10 to 1.69) compared with women who did not use cannabis during pregnancy. Infants exposed to cannabis in utero had a decrease in birth weight (low birth weight pOR=1.77: 95% CI 1.04 to 3.01; pooled mean difference (pMD) for birth weight=109.42 g: 38.72 to 180.12) compared with infants whose mothers did not use cannabis during pregnancy. Infants exposed to cannabis in utero were also more likely to need placement in the neonatal intensive care unit compared with infants whose mothers did not use cannabis during pregnancy (pOR=2.02: 1.27 to 3.21).

CONCLUSIONS AND RELEVANCE

Use of cannabis during pregnancy may increase adverse outcomes for women and their neonates. As use of cannabis gains social acceptance, pregnant women and their medical providers could benefit from health education on potential adverse effects of use of cannabis during pregnancy.

Vasopressin/V2 receptor stimulates renin synthesis in the collecting duct

Renin is synthesized in the principal cells of the collecting duct (CD), and its production is increased via cAMP in angiotensin (ANG) II-dependent hypertension, despite suppression of juxtaglomerular (JG) renin. Vasopressin, one of the effector hormones of the renin-angiotensin system (RAS) via the type 2-receptor (V2R), activates the cAMP/PKA/cAMP response element-binding protein (CREB) pathway and aquaporin-2 expression in principal cells of the CD. Accordingly, we hypothesized that activation of V2R increases renin synthesis via PKA/CREB, independently of ANG II type 1 (AT1) receptor activation in CD cells. Desmopressin (DDAVP; 10(-6) M), a selective V2R agonist, increased renin mRNA (∼3-fold), prorenin (∼1.5-fold), and renin (∼2-fold) in cell lysates and cell culture media in the M-1 CD cell line. Cotreatment with DDAVP+H89 (PKA inhibitor) or CREB short hairpin (sh) RNA prevented this response. H89 also blunted DDAVP-induced CREB phosphorylation and nuclear localization. In 48-h water-deprived (WD) mice, prorenin-renin protein levels were increased in the renal inner medulla (∼1.4- and 1.8-fold). In WD mice treated with an ACE inhibitor plus AT1 receptor blockade, renin mRNA and prorenin protein levels were still higher than controls, while renin protein content was not changed. In M-1 cells, ANG II or DDAVP increased prorenin-renin protein levels; however, there were no further increases by combined treatment. These results indicate that in the CD the activation of the V2R stimulates renin synthesis via the PKA/CREB pathway independently of RAS, suggesting a critical role for vasopressin in the regulation of renin in the CD.

Prazosin and propranolol in preoperative management of pheochromocytoma

Combined use of prazosin and propranolol was effective in preoperative management of three patients with norepinephrine(NE)-secreting pheochromocytoma (PHEO). On admission, all were symptomatic and had moderate to severe hypertension despite treatment with diuretics, propranolol, and sympatholytics. Optimal symptomatic and blood pressure (BP) control was achieved with 6 to 10 mg/day prazosin and 120 to 480 mg/day propranolol every 6 hr in equally divided doses. With this therapy, BP and hematocrit were reduced to levels similar to those found in the postoperative period. The daily urinary excretion of catecholamines and their metabolites was not modified during therapy with prazosin and propranolol. There was a drop in supine systolic (40 to 64 mm Hg) and diastolic (32 to 52 mm Hg) BP in all patients 1 to 2 hr after the first dose of prazosin (1-mg tablet); in two subjects this was accompanied by a larger orthostatic fall (74 and 92 mm Hg systolic; 65 and 78 mm Hg diastolic BP). The high incidence of first-dose effect suggests that a single oral dose of 1 mg of prazosin could aid in the diagnosis of PHEO. The effectiveness of prazosin in controlling the hypertension induced by NE-secreting PHEO suggests that, in man, pressure responses to augmented levels of NE are mediated solely through alpha 1-receptors.